1. Technical Field
The present invention relates to motors, and more particularly to a hollow motor module that reduces speed before outputting power.
2. Description of Related Art
FIG. 7 depicts a conventional motor module, which comprises a motor 8 and a speed reducer 9. The speed reducer 9 has its front section containing a speed-reducing gear set that includes a rotatory seat 91, planetary gears 92 and a sun gear 93. The planetary gears 92 are arranged in to a circle that they center the rotatory seat 91. The sun gear 93 is placed at the center of the planetary gear 92. The motor 8 has its output shaft 81 connected to the sun gear 93, so as to drive the sun gear 93 to rotate the planetary gears 92, thereby achieving first-stage deceleration. Then the rotatory seat 91 drives another speed-reducing gear set at the rear section (not shown) to operate. The speed-reducing gear set in the rear section is also composed of a sun gear and planetary gears like the one in the front section, so as to achieve second-stage deceleration.
In the conventional motor module as described above, only when the sun gear 93 of the speed-reducing gear set in the front section is connected to the output shaft 81 of the motor 8, the speed reducer 9 can decelerate the rotation of the output shaft of the motor. In addition, an additional sun gear has to be provided in the speed-reducing gear set in the rear section. These make the prior-art device need structural improvement.